//******************************************************************
//******************************************************************
//**********          ANts Peer To Peer Sources        *************
//
// ANts P2P realizes a third generation P2P net. It protects your
// privacy while you are connected and makes you not trackable, hiding
// your identity (ip) and crypting everything you are sending/receiving
// from others.

// Copyright (C) 2004  Roberto Rossi

// This program is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public License
// as published by the Free Software Foundation; either version 2
// of the License, or (at your option) any later version.

// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.

// You should have received a copy of the GNU General Public License
// along with this program; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.

package ants.p2p.query.security;

import ants.p2p.utils.encoding.Base16;
import org.bouncycastle.crypto.params.RSAKeyParameters;
import org.bouncycastle.crypto.params.RSAKeyGenerationParameters;
import org.bouncycastle.crypto.generators.RSAKeyPairGenerator;
import org.bouncycastle.crypto.AsymmetricCipherKeyPair;
import org.bouncycastle.crypto.engines.RSAEngine;
import org.bouncycastle.crypto.AsymmetricBlockCipher;
import org.bouncycastle.crypto.encodings.PKCS1Encoding;

import java.security.SecureRandom;
import java.math.BigInteger;
import java.io.*;

public class MessageHeader extends PublicHeader implements Serializable{
  SecureRandom sr = new SecureRandom();
  AsymmetricCipherKeyPair acKp;
  AsymmetricBlockCipher eng = new PKCS1Encoding(new RSAEngine());
  static final BigInteger  pubExp = new BigInteger("11", 16);

  public PublicHeader generatePublicHeader(){
    return new PublicHeader(this.exp,this.mod);
  }

  public MessageHeader(int size, int certainty) throws Exception{
    RSAKeyGenerationParameters param = new RSAKeyGenerationParameters(pubExp, sr, size, certainty);
    RSAKeyPairGenerator kpGen = new RSAKeyPairGenerator();
    kpGen.init(param);
    acKp = kpGen.generateKeyPair();
    RSAKeyParameters rsaParam = (RSAKeyParameters)acKp.getPublic();
    this.exp = rsaParam.getExponent();
    this.mod = rsaParam.getModulus();
    eng.init(false, acKp.getPrivate());
  }

  public BigInteger getExp(){
    return this.exp;
  }

  public BigInteger getMod(){
    return this.mod;
  }

  public String decryptSessionKey(String encryptedSessionKey) throws Exception{
    return Base16.toHexString(this.generate(Base16.fromHexString(encryptedSessionKey)));
  }

  private byte[] generate(byte[] encryptedSessionKey) throws Exception{
    return eng.processBlock(encryptedSessionKey, 0, encryptedSessionKey.length);
  }
}
